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<div class="moz-cite-prefix">Yves,<br>
<br>
I will track it down. Somehow (maybe correctly) an element of
about 1.0e-7 is being created by preprocessing. In most cases the
LPs are fine, but somehow in this case one LP is infeasible by
1.2e-7.<br>
<br>
As a temporary fix, I would switch off scaling and set the primal
tolerance to 5.0e-7. Either of these fixes problem on your
example - the second one should be all you need, but I don't think
it will do any harm to switch off scaling.<br>
<br>
I will get back to you when I have more to report.<br>
<br>
John Forrest<br>
On 08/01/14 14:55, Yves Touchard wrote:<br>
</div>
<blockquote cite="mid:52CD66D3.7070802@dxo.com" type="cite">
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John,<br>
<br>
I have the same kind of problem than (Vol78, Issue 6): swapping
two lines of the cost function to minimize modifies the solver
result (problem infeasible or not).<br>
<br>
What i did:<br>
<ul>
<li>Download the Cbc-2.8.8 archive (<a moz-do-not-send="true"
class="moz-txt-link-freetext"
href="http://www.coin-or.org/download/source/Cbc/">http://www.coin-or.org/download/source/Cbc/</a>Cbc-2.8.8.tgz)</li>
<li>Inflate it (tar xzf Cbc-2.8.8.tgz)</li>
<li>Copy the Vol78,Issue 6 fix you recently did: cp <a
moz-do-not-send="true" class="moz-txt-link-freetext"
href="https://projects.coin-or.org/Cgl/browser/stable/0.58/Cgl/src/CglProbing/CglProbing.cpp">https://projects.coin-or.org/Cgl/browser/stable/0.58/Cgl/src/CglProbing/CglProbing.cpp</a>
Cbc-2.8.8/Cgl/src/CglProbing/CglProbing.cpp</li>
<li>Build the binaries: ./configure -C; make; make test; make
install</li>
<li>Solve the attached problem: Cbc-2.8.8/bin/cbc test.lp ->
The problem is declared as infeasible</li>
<li>Swap lines 112 & 113 (those surrounded by blank lines)
and solve again -> The optimal solution is found.</li>
</ul>
<p>Obviously, i could remove these lines that are not used by the
cost function since mul coefficients are null. But, this
constraint file is generated by a piece of code and it is easier
to keep these unnecessary lines in the cost function (i expect
the solver ignore them). <br>
</p>
<p>Any help will be greatly appreciated.<br>
</p>
<p>Regards,<br>
</p>
<p>Yves<br>
</p>
<p><br>
</p>
<p><br>
</p>
<br>
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